Design and Analysis of Z-Trench-Assisted 9-LP-Mode Fiber With Low Differential Modal Group Delay and High Spatial Density

Abstract

We present a novel Z-trench-assisted (Z-TA) graded index 9-LP-mode fiber that significantly suppresses the maximum absolute differential modal group delay (Max $\vert $ DMGD $\vert$ ) while obtaining a high normalized spatial density (NSD). The finite element method (FEM) is applied for numerical simulations, and the results show that the Max $\vert $ DMGD $\vert $ is 18.9-ps/km at 1550-nm. To the best of our knowledge, it is improved by more than 30% compared to that of the theoretical optimal value in TA structure so far. Furthermore, the NSD of the proposed fiber can reach 44.64 at 1550-nm. Over the $C$ band, the Z-TA 9-LP-mode fiber exhibits Max $\vert $ DMGD $\vert < 32.6$ -ps/km, mode field area ( $A_{eff}) > 100~\mu \text{m}^{2}$ and low bending loss. In addition, the Z-TA structure is able to maintain relatively low degradation of DMGD characteristics when strict manufacturing variabilities are considered.

Keywords

• Few-mode fiber
• differential mode group delay
• Z-trench-assisted
• normalized spatial density
• mode division multiplexing